/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache Lucene" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache Lucene", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

using System;
using System.Text;

namespace DotnetPark.NLucene.Analysis.Standard
{
	/// <summary>
	/// Normalizes tokens extracted with StandardTokenizer.
	/// </summary>
	public class StandardFilter : TokenFilter
	{
		///<summary> Construct filtering <i>in</i>.</summary>
		public StandardFilter(TokenStream ts)
		{
			input = ts;
		}

		private static String APOSTROPHE_TYPE = Stc.tokenImage[Stc.APOSTROPHE];
		private static String ACRONYM_TYPE = Stc.tokenImage[Stc.ACRONYM];

		///<summary>
		/// Returns the next token in the stream, or null at EOS.
		/// <p>Removes <tt>'s</tt> from the end of words.</p>
		/// <p>Removes dots from acronyms.</p>
		///</summary>
		public override NLucene.Analysis.Token Next()
		{
			NLucene.Analysis.Token t = input.Next();

			if(t == null)
				return null;

			String text = t.TermText;
			String type = t.Type;

			if(type == APOSTROPHE_TYPE &&		  // remove 's
				(text.EndsWith("'s") || text.EndsWith("'S")))
			{
				return new NLucene.Analysis.Token
					(text.Substring(0, text.Length - 2),
					t.StartOffset, t.EndOffset, type);

			}
			else if(type == ACRONYM_TYPE)
			{		  // remove dots
				StringBuilder trimmed = new StringBuilder();
				for(int i = 0; i < text.Length; i++)
				{
					char c = text[i];
					if(c != '.')
						trimmed.Append(c);
				}
				return new NLucene.Analysis.Token(trimmed.ToString(), t.StartOffset, t.EndOffset, type);

			}
			else
			{
				return t;
			}
		}
	}
}
